Quality Evaluation of Topographic Data from SRTM3 and GTOPO30

High resolution digital topographic data is very essential for the scientific engineering tasks, e.g. fundamental GIS construction, EGM modeling and geoid determination. SRTM is a mission to collect digital topographic data with radar mapping technology by USA Space Shutter in February 2000. These global digital topographic data obtained by SRTM are with best accuracy, highest resolution and up-to-date till now. There are two kinds resolution of SRTM data: 3″×3″ (SRTM3) and 1″×1″(SRTM1). The global SRTM3 data have been declassified in the beginning of 2005. The vertical datum for SRTM3 is EGM96 geoid, and the horizontal datum for SRTM3 is WGS84. In SRTM3 the nominal absolute altitude accuracy is 16m, and the absolute plane accuracy is 20 m. The SRTM3 data cover a belt area between 60°N and 54°S on the Earth. Besides, the global DTM data provided by GTOPO30 are also briefly introduced in the paper. Different DTMs in the area between 60°N and 54°S obtained by SRTM3, GTOPO30 and ERS-1, ERS2 respectively have been compared with each other by France. The general comment is: the difference ≤±5 m is 56% of the SRTM3 data; the difference ≤±10 m is 86% of the SRTM3 data;the difference ≤±16 m is 88% of the SRTM3 data;the difference ≤±30 m is 98% of the SRTM3 data. Different DTMs in German area measured by SRTM3, GTOPO30 and German themselves, i.e. FRG-2B, respectively have been compared with each other by German. The average difference between SRTM3 and FRG-2B data is +2.7 m, and mean square error is 7.9 m. The average difference between GTOPO and FRG-2B data is -0.3 m, and mean square error is 27.68 m.